1. Field of the Invention
This invention relates to an infrared radiation gas analyzer for determining the concentration of a specified ingredient in a sample gas, which analyzer is simple and has an inexpensive construction from which an infrared light source and a power source for stabilizing the light source, previously required in a conventional infrared gas analyzer, have been eliminated. The analyzer heats a sample gas and measures the infrared radiation having characteristic wave lengths of the ingredient and radiated from the ingredient in the heated sample gas.
2. Description of the Prior Art
A nondispersive infrared absorption method has often been used for the determination of the concentration of an ingredient in a gas. This method utilizes Lambert-Beer's law, that is to say, the fact that the strength of infrared rays transmitted through the gas is reduced as a function of the concentration of the ingredient in the gas and the cell length as shown by the following equation (1): EQU I=I.sub.o exp.sup.(-kCl) ( 1)
in which
I: the strength of infrared rays after transmitting through gas; PA1 I.sub.o : the strength of incident rays; PA1 k: constant; PA1 c: concentration of the ingredient in the gas; and PA1 l: cell length
FIG. 1 shows one embodiment of a conventional infrared gas analyzer utilizing the nondispersive infrared absorption method. Referring now to FIG. 1, an infrared light source 1' having tungsten lamps or the like, has a light quantity balancer 2', and the lamps are directed through a sample cell 3' and a reference cell 4'. A chopper 5' is provided at the output ends of cells 3' and 4' and chops the emitted radiation falling on an infrared detector 6' such as a condenser microphone. In the nondispersive infrared absorption method carried out in this apparatus, the incident ray is from said infrared light source 1'. Any change in the quantity of light from said infrared light source 1' leads to errors of measurement, and consequently a power source for the light source must maintain the quantity of light from said light source 1' constant. The construction of the power circuit for such a power source becomes complicated and expensive. Moreover, when carrying out the nondispersive infrared absorption method, when using the reference cell 4', optical adjustment of the quantity of light incident upon both of said cells 3' and 4' is necessary for preventing drift owing to the deterioration of said light source 1' and fouling of said cell 3'.